The present invention relates to a wire bonding apparatus, and more particularly to a wire bonding apparatus which can apply high speed bonding to high density semiconductor integrated circuits.
In semiconductor devices, a bonding process is required in order to make an electrical connection between the semiconductor pellet and lead portions. A typical bonding method which has been implemented in the art is the wire bonding method. Ordinarily, a bonding pad on the semiconductor pellet and a bonding portion on the inner lead are interconnected by a bonding wire. The bonding wire is delivered to each wiring position by means of a capillary.
In recent years, other bonding methods, e.g., the TAB (Tape Automated Bonding) method and the CCB (Controlled Collapse Bonding) method, have been developed as a substitute for the wire bonding method. In accordance with the TAB method, the semiconductor pellet is mounted on a table and a bump is directly pressure-bonded to the inner lead without using bonding wire. In accordance with the CCB method, a solder ball is used to pass a portion subject to bonding through a furnace once to thereby cause collective bonding. The above-mentioned methods can advantageously perform the bonding for multi-terminal semiconductor devices, and they are gradually becoming accepted.
As stated above, the wireless bonding has been increasingly accepted in recent years, but wire bonding is still mainly practiced. This is because the wireless bonding generally has the economical restriction in that a work device at the side of the semiconductor pellet is required, resulting in necessity of purchasing new equipment, and there is the additional drawback with the TAB method that an uniformity in weighting and an uniformity of temperature are required in the case of implementing pressure-bonding, giving rise to technical difficulty. The drawback with the CCB method is that fatigue occurs during given temperature cycles because a solder is used.
For the reasons stated above, it is anticipated that the demand for the wire bonding apparatus will still increase, but will continue to be hampered by the drawbacks with the conventional wire bonding apparatus which are as follows.
(1) Bonding speed is slow.
As compared of the method to implement bonding of the entire pellet in a collective manner as in the TAB method or the CCB method, since wires are connected to the pellet one by one in the conventional wire bonding apparatus, the bonding time becomes lengthy as the number of terminals of the semiconductor device increase, thus constituting a serious hindrance for mass production.
(2) There is a limitation in the implementation at high density.
For realizing the high integration of the semiconductor device, the bonding pad pitch and the inner lead pitch must be reduced. However, a problem as described just below as pitches are thus reduced, and a pitch reduction becomes extremely difficult.
(3) Life time of capillary is short.
As stated above, the supply of bonding wires is conducted by using a capillary. Specifically, in the case of wedge bonding, the pressure-bonding portion of the capillary is always subject to strong impact. For this reason, damage will occur when used for a long time. In addition, since the width of the pressure-bonding portion must be reduced for realizing high density implementation as described above, the strength of this portion is further lowered, which tends to make the life time increasingly short.